This disclosure relates to polyetherimides and compositions containing the polyetherimides, as well as their method of manufacture and articles formed from the polyetherimide compositions.
Polyetherimides (“PEIs”) are amorphous, transparent, high performance polymers having a glass transition temperature (“Tg”) of greater than 180° C. PEIs further have high strength, heat resistance, and modulus, and broad chemical resistance, and so are widely used in applications as diverse as automotive, telecommunication, aerospace, electrical/electronics, transportation, and healthcare.
Polyetherimides can be manufactured commercially by a “halo-displacement process.” A halogen-substituted anhydride is reacted with a diamine to form a bishalophthalimide. The bishalophthalimide is then reacted with a metal salt of a dihydroxy compound. Despite extensive investigation into the manufacture of polyetherimides produced using the halo-displacement process, there nonetheless remains a need for further improvement. For example, chloro-displacement technology allows the ratio of the 4 and 3 ether linkages of the polymer to be significantly altered. The earlier nitration process is limited to high 4-isomer content, only a 95:5 isomer ratio of the 4:3 isomers can be obtained. The halo-displacement process allows for a polyetherimide material with any ratio of 4 and 3 ether linkages in the polymer; however, the halide level is above the 900 ppm level required for use in electrical/electronics applications.
There accordingly remains a need in the art for methods for the manufacture of polyetherimides having improved properties, in particular polyetherimides having improved Tg and flow, but with reduced levels of byproducts, including halogenated byproducts and cyclic byproducts. It would be a further advantage if such improvements were obtained without significantly adversely affecting other desirable properties of the polyetherimides, for example, one or more of heat deflection temperature, Vicat, and high tensile strength at yield.